This invention relates generally to novel compounds which are useful as precursors in the preparation of catalysts which effect the metathesis of olefins, including functionalized olefins and to novel methods for their preparation. More specifically, novel compounds in accordance with embodiments of the present invention comprise transition metal based complexes which provide a facile chemical synthesis to producing corresponding transition metal based catalysts. Such complexes may be represented by the following structural formula I EQU M(R.sub.1).sub.2 (NR.sub.2).sub.2 (R.sub.3).sub.x (I)
in which M, R.sub.1, R.sub.2, R.sub.3, and x are defined below.
In addition, the present invention also encompasses within its scope novel methods for the production of these complexes. These methods are more advantageous than prior methods because they are more economical in both the reaction time and the cost of starting materials.
The metathesis process can be defined as the redistribution of alkylidene moieties in a mixture of olefins. The simplest example is EQU 2R'CH.dbd.CHR.revreaction.R'CH.dbd.CHR'+RCH.dbd.CHR
The reaction proceeds by addition of an olefin to a catalyst having a metal-carbon double bond (M.dbd.CHR, a metal-alkylidene complex) to give a metal-lacyclobutane ring, which then releases an olefin to reform a metal-alkylidene complex. A typical olefin of interest which will undergo metathesis in the presence of catalysts having a metal-carbon double bond is an ester of oleic acid, cis-CH .sub.3 (CH.sub.2).sub.7 CH.dbd.CH(CH.sub.2).sub.7 CO.sub.2 H. Three of the most active metals used in classical olefin metathesis are molybdenum, tungsten and rhenium. (Ivin, K.J., Olefin Metathesis, Academic Press, London, 1983; Grubbs, R.H. in Comprehensive Organometallic Chemistry, Wilkinson, G. et al. (Eds), Vol. 8, Pergamon New York (1982); Dragutan, V. et al., Olefin Metathesis and Rinq-Ooeninq Polymerization of Cyolo-Olefins, 2nd Ed., Wiley-Interscience: New York (1985); Leconte, M. et al. in Reactions of Coordinated Lioands, Braterman, P.R. (Ed.), Plenum: New York (1986).)
Examples of molybdenum (VI) alkylidene complexes (Murdzek, J.S. and R.R. Schrock, Organometallics 6: 1373 (1987); Bazan, G. et al., Polymer Commun. 30: 258 (1989); Schrock, R.R., Murdzek, J.S., Bazan, G.C., Robbins, J., DiMare, M., and O'Regan, M., Synthesis of Molybdenum Imido Alkylidene Complexes and Some Reactions Involving Acyclic Olefins, J. Am. Chem. Soc. Vol. 112, p. 3875-3886 (May 9, 1990)) and tungsten (VI) alkylidene complexes have been previously described (Schrock, R.R. et al. in Advances in Metal Carbene Chemistry (Schubert, U. (Ed.), Kluwer Academic Publishers, Boston: 1989, page 323; Schrock, R.R. et al., Macromolecules 20: 1169 (1987); Ginsburg, E.J. et al., J. Am. Chem Soc. 111: 7621 (1989); Swager, T.M. et al., J. Am. Chem Soc. 111: 4413 (1989)
Several of these compounds have been shown to catalyze the metathesis of olefins with an activity that can be controlled through the choice of the alkoxide ligand. For example, molybdenum and tungsten catalysts reported by Schrock, R.R. (U.S. Pat. Nos. 4,681,956 and 4,727,215) have been shown to homogeneously metathesize at least 250 equivalents of methyl oleate.
Several rhenium alkylidene complexes have also been reported (Edwards, D.S. et al., Organometallics 2: 1505 (1983); Edwards, D.S., "Synthesis and Reactivity of Rhenium (VII) Neopentylidene and Neopentylidyne Complexes", MIT Doctoral Thesis (1983); Horton, A.D. et al., Organometallics 6: 893 (1987); Horton, A.D. and R.R. Schrock, Polyhedron 7: 1841 (1988); Cai, S. et al., J. Am. Chem. Commun., 1489 (1988). In particular, the Edwards references describe three rhenium complexes represented by the formula Re(C-t-Bu)(CH-t-Bu)(R).sub.2 where R is a t-butoxide, trimethylsiloxide or neopentyl moiety.
The catalysts may be produced by conventional synthesis techniques as described above. A way to achieve a desirable synthesis, is to employ a precursor which itself is both economically and easily prepared. Economy in the production of a precursor is reflected in cost of its starting materials, ease of handling its starting materials, length of reaction time and number of steps required to produce the precursors.
The compounds in accordance with embodiments of the present invention comprise precursors to the synthesis of catalysts which effect the metathesis of olefins, including functionalized olefins. Therefore, a principal object of the present invention is to provide precursor compounds which may be easily synthesized using low cost materials in as few steps as possible, thus lowering the overall cost for the production of the corresponding catalyst.